1,2,both battery switch query

[SAWDOC]

Can anyone provide a link as to how a1,2 both battery switch should be wired so as to have battery no1 as dedicated starter battery and no 2 as domestic battery. With this arrangement is there an advantage in turning the battery switch to both before attempting to start or if the domestic battery has been discharged could switching to "both" be counterproductive ?

Also am I correct in thinking I can start on 1 and then switch to both with engine still running without causing damage ?

 

[sarabande]

Vetus catalogue p 202 is useful.

http://viewer.zmags.com/publication/04e44322#/04e44322/202


If you need to use both batteries to start, then the engine battery is too small.


If you combine both batteries, with one of them dead, then you may almost certainly not have enough power to start the engine.


Battery switches usually go

1
Both
2
Off

if rotated in one direction. Some go 1, 2 Both, Off. The circuitry is arranged so that you never lose contact with at least one battery UNLESS you go to OFF then 1.

Switches do vary a little, though, in their selector protocols; some have additional protection. e.g.

http://www.bluesea.com/products/category/Manual_Battery_Switches/e-Series

 

[andygc]

Common goes to engine and alternator. 1 to battery 1, 2 to battery 2. Separate live feed from battery 2 via an isolator and fuse to your domestic distribution panel. (ie not from the common terminal like many boats, apparently, have - there's previous threads on this)

Start in position 1. If the starter battery is in good nick, switch to 2 after 10-15 minutes. No need to use Both position unless your batteries are both knackered and it's the only way you can get enough current to start. Connecting a depleted domestic to a good start battery with no charging current available is a particularly bad idea.

PS, sarabande, there's plenty of Off-1-2-Both switches on the market (which don't go back to off), but mine's an Off-1-both-2-and back to off.

 

[JumbleDuck]

Can anyone provide a link as to how a1,2 both battery switch should be wired so as to have battery no1 as dedicated starter battery and no 2 as domestic battery. With this arrangement is there an advantage in turning the battery switch to both before attempting to start or if the domestic battery has been discharged could switching to "both" be counterproductive ?

Traditionally, a 1-2-Both switch is used when you have a single electrical system for the boat (ie engine and domestic are all on the same circuit) but wish to connect to different batteries when the engine is off and on. Engine off: everything is connected to Battery 1. When you want to use the engine you change to Both in order to link in Battery 2. As the engine is running it charges both batteries and when you switch it off you go back to 1 again to make sure that you don't discharge both batteries with house loads. With that sort of system you don't really have to use 2 alone except in very odd circumstances, like a very short engine run with a flat domestic battery and an almost flat engine battery, in which case you're best to put everything into the engine one.

If you have some means of splitting the charge it's all a lot easier. You can do everything, including engine start, off the house battery and think of the other simply as an emergency reserve for starting. In that case the switch would sit at 1 all the time, save in emergencies.

I've just redone my boat with two completely separate systems, one for the engine and one for everything else. They're switched simultaneously with a dual circuit switch and can be linked if ever I need emergency power to a flat system. I think worries about paralleling charged and discharged batteries are unnecessary. I've just got in from jump starting a completely flat VW Golf 1.9 diesel from a puny Polo 1.0. Jump leads on, small spark at connection, turned Golf key, caught at once.

 

[VicS]

Can anyone provide a link as to how a1,2 both battery switch should be wired so as to have battery no1 as dedicated starter battery and no 2 as domestic battery. With this arrangement is there an advantage in turning the battery switch to both before attempting to start or if the domestic battery has been discharged could switching to "both" be counterproductive ?

Also am I correct in thinking I can start on 1 and then switch to both with engine still running without causing damage ?

This is the probably simplest way of wiring a 1, 2, both, type of switch, although neither battery is actually dedicated to either purpose

The engine circuits and the domestic circuits are both connected to the common terminal. One battery is connected to terminal 1 and the other ( in this case I have shown a bank of two batteries ) is connected to terminal 2.

1 is selected. The engine is started . After allowing the no1 battery to recharge the switch is turned to battery 2. the boat is now powered from battery 2 , which is also now being charged, until the engine is next started or the boat is shut down.

If necessary the domestic bank can be used for starting or the domestics run from the starter battery or even both 1 and 2 used in parallel.

Depending on the exact type of switch used it may be necessary to take care not to switch via the off position while the engine is running

 

[andygc]

The question was specifically how to have one bank as dedicated domestic, one as dedicated start. Answer: do not take a lead to "all boat circuits" from the common terminal on the switch. As I already said, take the engine connection from common, and take the domestic battery +ve via an isolating switch and fuse to the domestic distribution board. In VicS' s diagram, that is from the +ve terminal of the left hand domestic battery. That way, when you turn off the engine you can return the switch to 1 ready for your next start, but without draining your start battery by supplying your electrics. I fail to understand why anybody would want to wire a master switch so that the start battery can be accidentally discharged while sailing. By not having everything wired to common, there's no risk of accidental discharge unless you leave the switch on Both.

 

[JumbleDuck]

The question was specifically how to have one bank as dedicated domestic, one as dedicated start. Answer: do not take a lead to "all boat circuits" from the common terminal on the switch. As I already said, take the engine connection from common, and take the domestic battery +ve via an isolating switch and fuse to the domestic distribution board. In VicS' s diagram, that is from the +ve terminal of the left hand domestic battery. That way, when you turn off the engine you can return the switch to 1 ready for your next start, but without draining your start battery by supplying your electrics. I fail to understand why anybody would want to wire a master switch so that the start battery can be accidentally discharged while sailing. By not having everything wired to common, there's no risk of accidental discharge unless you leave the switch on Both.

There's no risk of an accidental discharge on the usual system (engine and domestic wired to 1-2-Both) either unless you leave the switch on Both. Your system seems to be more complicated than a either simple 1-2-Both or a dual+combine without the advantages of either.

 

[VicS]

The question was specifically how to have one bank as dedicated domestic, one as dedicated start. Answer: do not take a lead to "all boat circuits" from the common terminal on the switch. As I already said, take the engine connection from common, and take the domestic battery +ve via an isolating switch and fuse to the domestic distribution board. In VicS' s diagram, that is from the +ve terminal of the left hand domestic battery. That way, when you turn off the engine you can return the switch to 1 ready for your next start, but without draining your start battery by supplying your electrics. I fail to understand why anybody would want to wire a master switch so that the start battery can be accidentally discharged while sailing. By not having everything wired to common, there's no risk of accidental discharge unless you leave the switch on Both.

IMHO once you start to talk about dedicated batteries its time to throw out the 1, 2, both switch in favour of two separate isolator switches and an emergency linking switch together with a split charging system .

what you are suggesting may avoid accidentally discharging the start battery while sailing ( or just lounging in port or at anchor for that matter) but it also prevents you using the start battery for domestics should the need arise.

 

[JumbleDuck]

IMHO once you start to talk about dedicated batteries its time to throw out the 1, 2, both switch in favour of two separate isolator switches and an emergency linking switch together with a split charging system .

Agreed.

what you are suggesting may avoid accidentally discharging the start battery while sailing ( or just lounging in port or at anchor for that matter) but it also prevents you using the start battery for domestics should the need arise.

Agreed again. He's got an extra switch for less flexibility than a 1-2-Both and less foolproofness than a dual+combine.

 

[vyv_cox]

The question was specifically how to have one bank as dedicated domestic, one as dedicated start. Answer: do not take a lead to "all boat circuits" from the common terminal on the switch. As I already said, take the engine connection from common, and take the domestic battery +ve via an isolating switch and fuse to the domestic distribution board. In VicS' s diagram, that is from the +ve terminal of the left hand domestic battery. That way, when you turn off the engine you can return the switch to 1 ready for your next start, but without draining your start battery by supplying your electrics. I fail to understand why anybody would want to wire a master switch so that the start battery can be accidentally discharged while sailing. By not having everything wired to common, there's no risk of accidental discharge unless you leave the switch on Both.

Most people like to know that when the switch says 'off' it means off. In your suggestion there need to be two 'offs'. What could be simpler than leaving the switch on the domestic side (2) when sailing or at anchor, then switching to starter (1) when about to start? The worst that can happen then is that the domestic bank is not charged while the engine is running. I leave mine on (2) almost always, only starting the engine on (1) very occasionally and charging it for 30 minutes.

 

[chewi]

mine has the common to all circuits, I start on BOTH and usually leave it like that. If I anticipate my current draw could compromise the start battery I switch to DOMESTIC on arrival. I never need to switch while the engine is running so there is no risk of switching through OFF.

I haven't found myself out of battery like that yet.

Is there a downside to this that I'm missing?

 

[andygc]

The switches are next to each other. When the master switch says off, the engine cannot be started by an intruder unless they break into the boat, but my solar panel is still charging my battery so I am able to leave the fridge switched on. I don't have any problem working out when the domestics are off, the switch key comes out in my hand. I have no use for a VSR. The only time I need to charge the start battery is after starting, so I change to 2 when that's done. When I'm sailing I switch back to 1 so that I can start the engine from the start battery immediately without leaving the cockpit. Fitting a VSR would be a pointless expense in my boat, as would be throwing away my perfectly good 1-both-2-off switch to buy three switches to replace it.

I have no problems with my wiring, you have no problems with yours. I answered the OP's question, you didn't. He wanted to have dedicated batteries on a 1-2-both switch. Now he knows one way of doing it. If any of you know another way, why not tell him rather than telling me I'm wrong?

 

[chewi]

The switches are next to each other. When the master switch says off, the engine cannot be started by an intruder unless they break into the boat, but my solar panel is still charging my battery so I am able to leave the fridge switched on. I don't have any problem working out when the domestics are off, the switch key comes out in my hand. I have no use for a VSR. The only time I need to charge the start battery is after starting, so I change to 2 when that's done. When I'm sailing I switch back to 1 so that I can start the engine from the start battery immediately without leaving the cockpit. Fitting a VSR would be a pointless expense in my boat, as would be throwing away my perfectly good 1-both-2-off switch to buy three switches to replace it.

I have no problems with my wiring, you have no problems with yours. I answered the OP's question, you didn't. He wanted to have dedicated batteries on a 1-2-both switch. Now he knows one way of doing it. If any of you know another way, why not tell him rather than telling me I'm wrong?

was that directed at me?

I didn't say anyone was wrong. I just asked a question.

 

[JumbleDuck]

I have no problems with my wiring, you have no problems with yours. I answered the OP's question, you didn't. He wanted to have dedicated batteries on a 1-2-both switch. Now he knows one way of doing it. If any of you know another way, why not tell him rather than telling me I'm wrong?

OK then, simple answer: he can't have dedicated batteries with a 1-2-B. Dedicated batteries mean separate circuits mean separate switches, even if one of them is a reused 1-2-B. Are we in agreement?

 

[DJE]

OK then, simple answer: he can't have dedicated batteries with a 1-2-B. Dedicated batteries mean separate circuits mean separate switches, even if one of them is a reused 1-2-B. Are we in agreement?

Depends how you use the switch - and how you define dedicated!

 

[andygc]

was that directed at me?

I didn't say anyone was wrong. I just asked a question.

No, certainly not. My apologies if you thoughf it was. If you look at the time you'll see I was writing mine while you posted yours. I was responding to previous posters.

 

[andygc]

OK then, simple answer: he can't have dedicated batteries with a 1-2-B. Dedicated batteries mean separate circuits mean separate switches, even if one of them is a reused 1-2-B. Are we in agreement?

No, dedicated batteries means batteries dedicated to a single purpose. Like mine.

Depends how you use the switch - and how you define dedicated!

Exactly.

 

[SAWDOC]

Thanks to everyone who has contributed to this thread - I have learnt a good deal from the various comments. I had been inclined towards switching from off to both when starting - in future I will use either 1 or 2 more frequently only using both as a last resort. I agree with the suggestion to run everything off 2 when possible this seems to be practicable in my case at least with modest domestic use. On longer cruises, the start on 1 and switch to 2 after recharging Is more realistic if 2 has become discharged.
My interest in the topic has arisen from an incident where the switch was left on both with engine stopped and several appliances running - we just about managed to start the engine again. It would not turn over on both but did so on 1, which fortunately had not been discharged as much as 2, which had been used previouly for domestics.

 

[theoldsalt]

I have had a lot of electrical work done on my boat recently by what seems like a very professional and competant marine electrician.

During the work we had a lengthy discussion regarding what is meant by "a dedicated starter battery".

He convinced me that "a dedicated starter battery" should not be wired through a "1,2,both,off" switch but directly to the starter motor through it's own isolating switch. It is not connected to domestic in any way - hence the term "dedicated starter". Only domestic batteries should be wired through a "1,2,both,off" switch or alternativey their own isolating switches.

PS In an ideal world.

 

[Stu Jackson]

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615